As a work stand to set the trans on the floor (or ground)
I use a 4-foot length of 2x12 with a 3/4 hole bored into the middle of it.

The hole is for the input shaft which protrudes slightly from the bellhousing

with the trans standing on it's bellhousing with the tail shaft housing removed and using either a mototool or a "cape chisel" remove the "staked" portions of the two nuts on the tail shaft and countershaft.

Now lock the trans in two gears at the same time (With the top cover off push both the 1-2 and 3-4 synchro collars "down")

Using the two LONG bellhousing bolts at the
10 O'clock and 3 O'clock positions to prevent the tranny from rotating use a pipe wrench to remove the main shaft nut.

If you don't have a pipe wrench use a large chisel against the flats of the nut to drive it off (the nut is not re-usable anyway)

Repeat procedure for countershaft nut though for that you may actually have the 30mm socket you'll need.

Now, flip the trans bellhousing up (a garbage pail half filled with paper makes a nice work stand) remove the front bearing retainer.

Remove trans from garbage pail and put it back on the wood block.

Using a pry bar to apply upwards force on the rear bearing strike the end of the output shaft with a brass or lead hammer.
Rotate shaft between blows until you get the bearing off.

At this point it's all 12mm socket work and simply disassembling things in sequence, but will generally get you into whatever parts you have screwed up.

if there are any questions, ask them and I'll revise this as needed...